As a concept, “Pride and Prejudice and Zombies” is the sort of absurd brainstorm that won’t just sit on the page. The phrase almost giggles for you; we were doomed to experience it the moment it became a repeatable thought. The 2009 novel by Seth Grahame-Smith reworks Jane Austen‘s 1813 novel just enough to amplify the heroic qualities of a few characters into modernity, with some social conflicts replaced with zombie battles. And ninjas. The book also has a bunch of ninjas.

The ninjas didn’t end up in this film, but the movie directed by Burr Steers (“Charlie St. Cloud,” “Igby Goes Down“) keeps much of the rest of the span of Grahame-Smith’s revamp, with Lily James delivering a muscular and effective star performance as Elizabeth Bennet.

“Pride and Prejudice and Zombies” is not a particularly good zombie movie, and it is never an inventive one. Nor is it much of a comedy, despite scenes that lean well into camp. It’s a very slightly better play on Jane Austen, as the inherent draw of Austen’s original text is complemented in some ways by James’ performance and the modern genre sensibilities that inform her version of Elizabeth Bennet.

To breeze through it all: Elizabeth Bennet is the second of five Bennet daughters and their parents ardently seek suitable husbands for all. The arrival of Mr. Bingley (Douglas Booth) causes a stir amongst local society; the new guy is handsome, rich, and single. In a moment, he falls for Elizabeth’s older sister, Jane (Bella Heathcote), while Elizabeth begins a tentative and suspicious dance with Bingley’s protector, the prickly Mr. Darcy (Sam Riley).

So far, so Austen. In this version, however, the Bennet women have been taught to fight in China, the better to survive encounters with zombies, which have plagued England to the degree that London is now a walled-off city with a moat around it. Darcy’s preoccupation is not class or status, but — you guessed it — zombies. He skulks through fancy society parties equipped with a vial of carrion flies, the better to suss out whether any of the landed gentry might actually have crawled right out of their ancestral graves.

These zombies do not become insane brain-eating monsters until after they’ve had their first brains — prior to that they’re self-aware and somewhat intelligent, possibly able to pass for “normal.” Finding those hidden creatures keeps Darcy busy, but Elizabeth soon distracts this goth prince.

With zombies that can pass for human you’d be forgiven in thinking the creatures serve as a symbol — for the repressive social mores of the Regency Era, perhaps, or the poor. That should be the idea; zombie movies are far more potent when the undead serve a significant thematic purpose. But sadly, no such texture exists. These walkers mostly act as provocation: for the Bennet women to break away from social rigidity, and for the movie to exist.

Which makes “Pride and Prejudice and Zombies” less a zombie movie than a movie with zombies in it, a narrow but not insignificant distinction which does not explain why so little imagination is dedicated towards putting the undead on screen. A bit of inventiveness would go a long way here, but the charms of say, “Dead Alive” or “Shaun of the Dead” are absent.

Regardless, Lily James plays her part with buoyant determination and a fierce glint in her eye. The “strong female character” can be unsatisfying when she’s just another underwritten supporting role with a strong sword arm, but this Elizabeth Bennet is outspoken, determined, smart, and compelling. She could be the justified focus of a movie without the zombies, which in this case helps make the monsters feel quite redundant. A great many things in “Pride and Prejudice and Zombies” don’t work well at all, but James works so well that it’s almost an even game.

Elizabeth Bennet duels with many creatures, but the only fight that earns any real traction is with Mr. Darcy himself, as their evolving interests are aired and developed, naturally, through a fight scene. Sam Riley’s Darcy is as tightly corked as a bottle of wine the host forgot to open, but he’s a fine foil for James, and their scene is among the few that gets close to the ridiculous promise of the title concept.

More finely honed comic instincts, spread through the movie, would help. Towards the end, two characters battle seemingly for hours as their duel begins in full dark and ends in full daylight. There’s no sign of fatigue from either man, and no acknowledgement of this, no wink, no nod. Playing Mr. Collins, on the other hand, Matt Smith winks too broadly and too often; he performs with the twirl of a man constantly donning a cape. He is not dour, however, and is certainly entertaining, if awkwardly so by virtue of feeling out of place with everyone else.

Generally speaking, this film has no ability to modulate tone, no fine control over tenor. It lurches from head-splattering violence through comedy into drama with all the elegance of a rubber sea monster waddling on land. It is shriekingly loud but never surprising; goofy, but rarely funny. While handsomely crafted from the perspective of costume and production design, staging is conceived without any apparent awareness of subtlety. Then again, the film is called “Pride and Prejudice and Zombies” so perhaps subtlety was off from the beginning. [C-]